The platform is a quad-core Calxeda EnergyCore ARM SoC. Each chip draws only 5 Watts at full load, with eight chips weighing in at just 40 Watts. The circuit to power the server started as a solar charger, which was easy to convert just by transitioning from panels to a generator that works just like a bicycle trainer (the rear wheel presses against a spin wheel which drives the generator shaft).

So, the bicycle generator powers the solar charger, which is connected to an inverter that feeds a UPS. After reading the article and watching the video after the break we’re a bit confused on the actual setup. We would think that the inverter would feed the charger but that doesn’t seem to be the case here. If you can provide some clarity on how the system is connected please feel free to do so in the comments.

Pretty straightforward. The dc generator (or solar panels) feed their DC power production to the charger. The charger keeps a deep cycle 12V battery topped off, sending excess electricity that is not immediately used by the server or the battery to a fan.

The Server needs AC power, so the DC power of the generator / charger / battery trio is fed through a dc to ac inverter and then cleaned up a bit with a small UPS before hitting the server itself.

This way you have clean AC power at the server, with reservoirs of excess power in the UPS and DC battery, from an intermittently strong DC power source.

Interesting that this also offers feedback to the cyclist – if the fan is running, you are working too hard!

Further: I’m, surprised they went with the DC>AC>Server route, I would have expected a specific use system like this to go with a DC – DC power supply in the server, and skip the inverter / UPS stages entirely

So bear in mind “they” is me. I thought it was vaguely possible to pull off this hack by burning a lot of midnight oil. This wasn’t something for a commercial product offering, just for a demo during Red Hat Summit. If I were doing this as a commercial offering, there’s lots of other things I would do with the design. But I’m glad the point about the low energy future has been made!

You’re exactly right in the configuration I used (and the reasoning why). The bicycle is a drop-in replacement in a circuit that otherwise looks a lot like you’d see in a solar charging configuration. The Pedal-A-Watt generates power, which is fed through the charge controller that diverts excess load to the fan, and charges a battery. The battery is connected to an inverter that charges a UPS (smoothing sine wave) that then powers the server itself. The inverter doesn’t feed the charger because the charger is operating at DC level voltage and handling the diversion aspect. The fan was a hack to have a divert load that also provided amusement, but the one problem with it is that it’s a light load so when on divert the bike becomes very easy to pedal suddenly. When I move this to a sitting desk configuration (the plan for the rig after the demo) at home, to complement my standing desk I already use, I’ll balance the divert load more.

In fact, there will be a YouTube video of the entire presentation, with demo, very shortly ( http://www.youtube.com/redhat ), and in there you can see that the fan is running most of the time. A reality of live demos is that they never quite go to plan. In the live demo, the battery was already charged and the charge controller decided to keep on divert most of the time, so the power output was lower than 100W. After the demo, we had two days of people coming and riding the rig and generating up to 200W of power. Enjoy.

I thought the article was great. smilr seems to have the setup correct. Bicycle generator feeds a charger that charge a 12V battery and dumps any excess energy to a fan. The 12V battery powers a “cheap” inverter which generates the standard A/C voltage for the server but to protect their expensive server they passed it through a UPS first to ensure the voltage was clean. If they had used a better inverter they could have skipped the UPS or they could have used a line conditioner. Either way, after I read the article, I’m planning on trying to figure out if I can turn a motor from a cordless drill into a DIY “Pedal-A-Watt” and do something similar to power a nettop computer.

Yeah I’m no expert but I have Made a massive battery store (10* 105ah 12v batteries) with solar and water generation. And I found most inverters to be about 85% efficient, I’m sure there would also be a drop in efficiency for each battery that the power has to pass through. They would be better off not inverting & getting shot of that UPS. Dc to Dc would be the way to go.

1) SPS(“UPS”) and UPS(“true UPS”) are not the only power topoligies possible although they are the only consumer level solutions.

2) ditch the standard UPS and go with a DC-DC UPS… cut out the AC>DC>AC part and then you can use a topology with some fancy term that varies from place to place but the main point is how it actually works…
efficently with ***_ZERO_*** transfer time

im NOT talking about floating the battery at it’s full charge(ing) voltage! that will sulfate it in 1-5 years! im talking about one of the more complicated topoligies, where the battery is slow charged independant of DC output voltage and has ***_ZERO_*** transfer time so it actually does its job.

PS:
UPS (“true UPS”) causes battery to sulfate after few years and is not very efficent
SPS (“UPS”) has a switchover time, and for me is only useful for lighting or a stereo or things with built-in mini-UPSs.
in other words SPS is garbage and can be worse then an outright power loss.

MOST 50$ “UPS”s are ***_ACTUALLY_*** SPSs
and i dont care what you think about it.
its a fact. get used to it.

The correct terms for what you are describing are Online (sometimes called Double Conversion) and Offline (sometimes called Standby.) Wiki has some nice articles for people who want to know more about UPS units.

That said, this demo wasn’t as power efficient as it could have been. Ditching the two inverters (one in UPS, one off generator) and installing a switch mode DC PSU in the computer would have returned a 25% or so increase in efficiency. The demo still made its point.

At the AAPEX show in Vegas a few years ago, a vendor that sold re manufactured automotive alternators had 10 spandex clad bikers pedaling away on bikes rigged up to their alternators and in charge powering a live DJ session. It was kind of cool except for the foul body oder after 2 hours. Glad my booth wasn’t close by.

Scared of a little BO or are you scared that other people are working out more than you are? [;D]
I want to use this idea to power my netbook {Which barely consumes 50 watts} while I play minecraft. I got the bike, now I need the rest of the stuff.